Re: [PATCH v2 2/5] pack-objects: reset kept-pack cache for cruft walk

[Junio C Hamano <gitster@pobox.com>]

Qin ShiCheng <qeesung@live.com> writes:

> This does not make the code work with another backend -- nothing
> around it would either -- but pack-objects no longer gains a new
> dependency on the files backend, and the downcast sits with the
> others that will have to move together.

OK.

>> Do we need a similar
>> rearchitecting of the code here, pushing details like packfile
>> management down to the files backend layer, before we can properly
>> fix this?
>
> I hope not. Without this patch, a cruft repack with an expiration
> drops objects ...

Ah, I think you misunderstood.

By fix "this" I meant fixing "the layering violation" and not what
your topic originally wanted to achieve.  And as we agreed above,
these downcasts that sit together with existing ones need to move in
order to avoid layering violation, which is what I meant by
"rearchitecting".  Until that happens, layering violation is left
unfixed, but addressing the kept pack cache issue with layering
violation can be better than not addressing the issue at all.

In any case, my original question to experts

>> This question is primarily meant for folks who are pushing different
>> ODB backends, but I am not sure this is safe in the long term.

still stands.  I think we between two of us agreed the answer is "no
it is not safe in the long term", but others may have ideas to solve
it more cleanly, hopefully.

Thanks.